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[seuzy8]

I recently had Comcast Internet installed, and they hooked me up with an xfinity router. I quickly realized I had some problems while using wireless on my Ubuntu computer. I could always connect to the network, but I could only intermittently access the Internet. My computer reports being connected to the Wi-Fi, but whenever I try to visit a website, I am told that the server was not found. Everything is working fine on my Windows computer, which I am typing from.

Any ideas on how I can fix this? If you need more information on the problem, let me know.

Thanks!

[Baric]

What version of Ubuntu?  What kind of wireless adapter?  Run "dmesg" and tell us what is says for the your wireless hardware.  Run and post "ipconfig -a" and "iwconfig".

If the signal is intermittent, how far away are you from your wireless access point?  Have you tried changing the wireless channel on the access point?  What kind of wireless ecryption are you using?

[seuzy8]

Version is 12.04. Wireless adapter is Realtek RTL8188CE.

dmesg output:

http://pastebin.com/SJyjqU1H

Assuming you meant ifconfig -a:

eth0      Link encap:Ethernet  HWaddr 00:21:cc:63:55:ee  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:4899 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4275 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:5062355 (5.0 MB)  TX bytes:816265 (816.2 KB)
          Interrupt:20 Memory:f2600000-f2620000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:4603 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4603 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:376718 (376.7 KB)  TX bytes:376718 (376.7 KB)

wlan0     Link encap:Ethernet  HWaddr 68:a3:c4:c8:97:27  
          inet addr:10.0.0.3  Bcast:10.0.0.255  Mask:255.255.255.0
          inet6 addr: fe80::6aa3:c4ff:fec8:9727/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:392681 errors:0 dropped:0 overruns:0 frame:0
          TX packets:231439 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:562942153 (562.9 MB)  TX bytes:24174735 (24.1 MB)

and lastly iwconfig:

lo        no wireless extensions.

wlan0     IEEE 802.11bgn  ESSID:"Fortress"  
          Mode:Managed  Frequency:2.412 GHz  Access Point: 00:1D:D1:7E:A9:80   
          Bit Rate=65 Mb/s   Tx-Power=20 dBm   
          Retry  long limit:7   RTS thr=2347 B   Fragment thr:off
          Power Management:off
          Link Quality=56/70  Signal level=-54 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:15   Missed beacon:0

eth0      no wireless extensions.

The signal itself is not intermittent. I can get a WiFi signal at all times, but the connection refuses to load any webpages. (It's not a browser issue. I have tried several, and non-browser things such as apt-get update don't work.) I can still get on the router settings/admin page and so forth.

EDIT--Just realized I missed some of your questions. Distance from the access point should not be an issue (not far at all). I don't what it means or how to change the wireless channel and therefore have not done so. Encryption is WPA.

[Baric]

To change the wireless channel and encryption setup, log into your router and make those changes.  Encryption should be WPA2, not WPA.  Since you have not said what router you have, it's impossible to give explicit instructions, but in general, RTFM.  The manual should tell you how to do all of this. 

Your router is sitting at http://10.0.0.1.  Is it one of those Xfinity Wireless Gateways?  Ick and double ick.  I highly recommend getting rid of it ro having it bridged by the support folks at 800-363-2416 and use your own wireless router.  If you want to use, then definitely go and change the wireless security to WPA2PSK-AES and try again.  If no joy, change the channel for automatic to manual and try the various channels (remember to SAVE SETTINGS after each change).  The manual for the Xfinity gateways is here:

http://media2.comcast.net/anon.comcastonline2/support/userguides/Wireless_Gateway_User_Guide_030811....

Is "Fortress" your wireless network?  If so, that's not the default name, so someone has modified settings on this device.

[seuzy8]

The encryption was on an ambiguous setting that might have actually been some form of WPA2. I changed it to exactly what you suggested, but it did not affect the issue.

Yes, it is an Xfinity Wireless Gateway. They didn't give me a manual with it, and the one you linked to has no instructions for changing channels, but I'll maybe hunt around further for how to do that.

Since this situation is only for three months, I'd like to avoid purchasing a router, but I'll take your expressions of disdain for the gateway under advisement.

"Fortress" is the SSID that I manually set.

[Barmar]

It looks like your wireless is connecting properly -- you're getting a proper IP from the gateway's DHCP server. I assume you have no problem logging into the gateway's management page at 10.0.0.1.

My guess is it's a DNS issue. Post your /etc/resolv.conf.

It's also possibly a routing problem. Post the output of "netstat -rn".

[seuzy8]

Yes, I have no problem logging into 10.0.0.1.

resolve.conf:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.0.1
search hsd1.in.comcast.net

netstat -rn:

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         10.0.0.1        0.0.0.0         UG        0 0          0 wlan0
10.0.0.0        0.0.0.0         255.255.255.0   U         0 0          0 wlan0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 wlan0

[Baric]

Barmar may be correct.  This all looks correct, Ubuntu 12.04 uses a dnsmasq setup to get to the DNS servers.  What does /var/run/nm-dns-dnsmasq.conf say?

Under System Settings... -> Network, select your wireless connection and tell us what it says on the right side of the pane.  Then press  Options and tell us what is says on the IPv4 Settings tab. 

[Baric]

---

seuzy8 wrote:

Yes, it is an Xfinity Wireless Gateway. They didn't give me a manual with it, and the one you linked to has no instructions for changing channels, but I'll maybe hunt around further for how to do that.

---

Page 17, Channel Selection to Manual, pick a channel, and press SAVE SETTINGS.  You might also have to reboot to pick up the change.

[seuzy8]

/var/run/nm-dns-dnsmasq.conf:

server=75.75.75.75
server=75.75.76.76

Right side of the network pane says:

Wireless Connected - 65 Mb/s

Hardware Address 68:A3:C4:C8:97:27

Security WPA2

Network Name Fortress

IP Address 10.0.0.3

Default Route 10.0.0.1

DNS 75.75.75.75 75.75.76.76

IPv4 Settings tab says:

Method: Automatic (DHCP)

Addresses box is grayed out and empty

DNS servers field is grayed out and empty

Search domains field is grayed out and empty

DHCP client ID field is empty

Require IPv4 addressing for this connection to complete check box is not checked

EDIT--I tried changing the channel. It didn't help.

[seuzy8]

A few more things to note:

I've tried a wired connection to the gateway, and I get the same problem. Even when I shut off the wireless connection and the wired connection is the only one. This leads me to believe it shouldn't be a wireless card / driver issue and has something to do with the more general network settings of either the gateway or my laptop.

When I switch to the Windows partition of the same machine, I don't have any of these problems. And, as mentioned earlier, my other Windows laptop works fine.

I would get behind the idea that the problem is DNS-related. The step that Firefox always freezes on when getting a webpage is "Looking up foobar.com"

[Baric]

That DNS setup looks good and what I would expect as normal.  What happens when you do a "dig www.google.com"?  Do you get a good IP address back?  If so, it's likely not a DNS issue and I would look at possible proxy setups in your browser.  Are you using Firefox?  If so go to Edit -> Preferences -> Advanced -> Network and press the Settings... button and tell us what proxy settings you have.  If using "Use system proxy settings", go back to System Settings... -> Network, select Network proxy and tell us what is says on the right side of the pane.  Under normal circumstances, Method should be set to "None"

[seuzy8]

The problem is almost certainly DNS-related.

The output of dig www.google.com (without implementing the fix described below) is:

; <<>> DiG 9.8.1-P1 <<>> www.google.com
;; global options: +cmd
;; connection timed out; no servers could be reached

While I was hunting around about DNS problems on Linux, I came across something that actually fixes the problem, but it's an imperfect and hacky fix. If I add the following lines to my resolv.conf:

nameserver 8.8.8.8

nameserver 8.8.4.4

Everything works fine. My understanding is that this gives access to the Google DNS servers. However, resolv.conf is occasionally overwritten (as made obvious by the really loud comment the file contains), and I would like to implement a solution that is a one-time fix. However, I'm not sure exactly what I'm doing or why this works, so I give this information so that someone else more skilled may help me reach that solution.

[seuzy8]

Slightly updated solution that I'll post for anyone else having this problem:

To avoid having the changes to resolv.conf overwritten, there are a variety of solutions that you can simply search for. I chose to put my changes in the header file which is always written to resolv.conf. This file is in /etc/resolvconf/resolv.conf.d/head.

I would call this problem solved. Thanks to everyone who helped.

[Baric]

Well, I would disagree.  The problem is still there, you just short-circuited it.  If you use 75.75.75.75 and 75.75.76.76 I'm pretty sure it would work as well.  If so, that indicates your problem is local with Ubuntu and likely some kind of issue with dnsmasq either not running or not working properly.  Your dnsmasq file was correct (it is the same as mine which works here) but that file is only read/used by dnsmasq.  Your original /etc/resolv.conf was also like mine (and every other 12.04 user), pointing at the your own system for name resolution (also normal for 12.04) which only works if dnsmasq is running and working.  By changing resolv.conf (or the headers for generation), you are pointing directly as specific DNS servers (and not even Comcast's), so it doesn't matter that there's something wrong with your dnsmasq setup.  And that problem is still there.

While your system now resolves names to IP addresses again, it's not fixed.  If this were me, I would want to know WHY it's not working and fix that problem.  Where there's one problem, there may be others...

[msven]

I'm actually experiencing the same exact issues that he was describing.  I have a windows machine sitting right next to me and it has ZERO connectivity issues while my Ubuntu 12.04 machine is randomly unable to resolve names for 30seconds to 1.5 minutes.  All of a sudden it starts working again with no known reason.  For a test, I a added the Comcast DNS serves to /etc/resolvconf/resolv.conf.d/head.  I'd love to know WHY it is doing it but for right now, a fix will make me happy.

[msven]

So far it looks like adding the Comcast servers to /etc/resolv.conf has fixed the issue.  I added it to /etc/resolvconf/resolv.conf.d/head as well..Before, the below two lines were the only active entries and I guess (though I hate to use that word in IT troubleshooting) there was simply a resolution error using hsd1.ga.comcast.net.

nameserver 127.0.0.1
search hsd1.ga.comcast.net

[seuzy8]

Yep, that sounds like exactly the problem I had. I'm still using the fix described earlier, but if you ever figure out why it does that, definitely let me know.

[Barmar]

Is dnsmasq running? Use: ps ax | grep dnsmasq

[Tony124]

I just signed up with Comcast and was suddenly have the same problem.  dnsmasq in now running by default on Ubuntu 12.04 and is designed to resolve hostnames locally.  Here is how to disable it:

http://www.ubuntugeek.com/how-to-disable-dnsmasq-in-ubuntu-12-04precise.html

[soynog]

I too have been having this problem! I recently installed Ubuntu 12.04 alongside Windows 7 on my Lenovo Y530 Ideapad, and I have exactly the same intermittent internet issues described above. Windows 7 works fine, and at least one public wireless service that I tried out works fine. Wired connection has the same difficulty.

[soynog]

Update: Tony's fix seems to have worked for me. Thank you Tony! You're very dePANDAble.

Question: Will disabling dnsmasq affect my performance at all on other networks?

[Tony124]

Soynog,

I don't have enough knowledge to answer a performance question.